Combustion chamber for a gas turbine plant

ABSTRACT

A combustion chamber ( 1 ) for a gas turbine plant, has a combustion chamber wall ( 10 ), which is flowed through by combustion gases in the direction of a downstream expansion turbine, the chamber wall ( 10 ) has a device ( 20 ) for damping thermoacoustic oscillations caused by the combustion gases. At least one resonator tube ( 22 ), interacts with the resonator volume ( 21 ) and opens out into the combustion chamber ( 1 ) with its mouth (M) opposite from the resonator volume ( 21 ) in the combustion chamber inner wall ( 10 ). At least one feed opening ( 23, 23′, 23″ ) for sealing air for sealing the resonator tube mouth (M) is introduced into the combustion chamber ( 1 ) from a compressor plenum ( 2 ), surrounding the combustion chamber. The at least one first feed opening ( 23′, 23″ ) is provided in a region of the combustion chamber wall ( 10 ) close to the resonator tube mouth (M) and is aligned such that the sealing air (S) through the feed opening ( 23′, 23″ ) flows over the resonator mouth (M).

The invention relates to a combustion chamber for a gas turbine plantaccording to the preamble of claim 1 and to a correspondingly designedgas turbine plant according to claim 7.

Gas turbine plants are composed essentially of a compressor, of acombustion chamber with a burner and of an expansion turbine. In thecompressor, sucked-in air is compressed before it is mixed with fuel inthe combustion chamber in the following burner arranged in thecompressor plenum, and this mixture is burnt. The expansion turbinefollowing the combustion chamber then extracts thermal energy from thecombustion exhaust gases which have occurred in the burner and convertsthis into mechanical energy. A generator capable of being coupled to theexpansion turbine can convert this mechanical energy into electricalenergy for current generation.

Nowadays, gas turbine plants, like other current-generating plants, too,must have as low pollutant emissions as possible in all load ranges,while working at maximum efficiency. Major influencing variables are inthis case the mass flows, set in the combustion chamber of the burner,of the fuel, of the compressed air and of the cooling air delivered forcooling the burner components. However, the limitation of pollutantemissions, in particular of NOx and unburnt fuel mostly in the form ofCO, may lead to a minimization of the quantity of cooling air or ofleakage air in the combustion chamber and consequently to parasiticflows which have an acoustically damping effect. Furthermore, under theboundary condition of limiting the emissions, an increase in efficiencyusually also entails an increase in the volumetric heat release densityin the combustion chamber. The two together, that is to say a reductionin acoustic damping and an increase in the heat release density in thecombustion chamber, lead to a higher risk that thermoacousticallyinduced vibrations commence. However, thermoacoustic vibrations of thiskind in the combustion chamber present a problem in the design and, inparticular, in the operation of gas turbine plants.

To reduce such thermoacoustic vibrations, Helmholtz resonators, whichare composed of at least one resonator tube and of a resonator volume,are employed nowadays for damping. Helmholtz resonators of this kinddamp the amplitude of vibrations with the Helmholtz frequency inspecific frequency ranges as a function of the cross-sectional area andthe length of the resonator tube and of the resonator volume. Helmholtzresonators as damping devices for limiting thermoacoustic vibrations incombustion chambers are known, for example, from EP 1 605 209 A1 or U.S.2007/0125089 A1.

FIG. 1 shows, for example, the arrangement, known from U.S. 2007/0125089A1, of Helmholtz resonators 20 on a ring of the combustion chamber wall10 transversely to the flow direction. The combustion chamber wall 10 isin this case of tubular form and separates the combustion chamber 1 fromthe surrounding compressor plenum 2. The perforations 22 in thecombustion chamber wall 10 between resonator volume 21 and combustionchamber 1 form the resonator tubes of the Helmholtz resonators. In thiscase, as illustrated in FIG. 1, each Helmholtz resonator may have aplurality of resonator tubes or else only a single resonator tube. Sothat none of the hot combustion gases from the combustion chamber 1 areintroduced into the Helmholtz resonators 20, additional ports for thedelivery of barrier air are provided. In the exemplary embodiment shownin FIG. 1, these delivery ports 23 are arranged on that wall of theresonator volume 21 which lies opposite the resonator tubes 22. Theseports 23 make it possible that compressed air S can flow out of thecompressor plenum 2 surrounding the combustion chamber into theresonator volume 21 and from there, via the resonator tubes 22, into thecombustion chamber 1, thus barring the penetration of hot combustiongases into the resonator tubes 22.

However, Helmholtz resonators with deliveries of barrier air via thevolume body have the disadvantage that this barrier air flowing throughthe Helmholtz resonator can diminish its damping properties such thatinstabilities may occur when the burner is in operation. In particular,in such systems, even a marked reduction in the damping properties hasbeen found with an increasing velocity of the barrier air flowingthrough the resonator tubes. However, a specific barrier air velocity inthe resonator tubes is necessary in order to bring about a reliablebarrier effect with respect to the combustion gases entering theresonator from the combustion chamber. Moreover, this type of deliveryof barrier air makes it necessary to introduce from the compressorplenum a large fraction of air which, however, is then no longeravailable for actual combustion so as to reduce the flame temperature.This, in turn, in gas turbine plants operated at their power outputlimits for maximum NOx reduction, may bring about a rise in harmful NOxpollutants, although this is what is precisely to be avoided. Moreover,the cooler barrier air from the resonators may cause local instabilitiesin combustion to occur, thus leading in turn to increased CO pollutantemission.

The object of the invention is to provide a combustion chamber whichovercomes the disadvantages described above.

This object is achieved by means of the combustion chamber having thefeatures of claim 1.

Since a combustion chamber designed according to the preamble of claim 1and having at least one Helmholtz resonator has at least one deliveryport which is provided in a region of the combustion chamber wall nearthe resonator tube mouth of the at least one resonator tube and isoriented such that the barrier air flowing through the delivery portflows over the resonator mouth, the injection, known from the prior art,of barrier air through the Helmholtz resonator may be dispensed with.Its damping properties are therefore no longer influenced by the barrierair flowing through, with the result that reliable damping ofthermoacoustic vibrations is achieved, thus ultimately lengthening theservice life of the combustion chamber and therefore of the entire gasturbine plant. Moreover, with the barrier air delivery designedaccording to the invention, less air from the compressor plenum isrequired, as compared with the known versions, so that, overall, the NOxand CO pollutant emission of the gas turbine plant also becomes lower.

Further preferred exemplary embodiments may be gathered from thesubclaims. What is essential in all the combustion chamber versions isthat, with the aid of suitably designed delivery ports, a barrier filmis built up in front of the resonator tube mouths on the combustionchamber side, and barrier air can thus be used more effectively as areliable barrier against the inflow of hot combustion gases from thecombustion chamber into the Helmholtz resonators, and at the same timethe damping properties of the Helmholtz resonators are not influenced bythe barrier air. Gas turbine plants equipped with such combustionchambers can thus have as low pollutant emissions as possible in allload ranges, while working at maximum efficiency.

The invention, then, will be explained by way of example by means of thefollowing figures in which:

FIG. 1 shows diagrammatically a damping device known from the prior art,

FIG. 2 shows diagrammatically a first version according to the inventionof a damping device,

FIG. 3 shows diagrammatically a second version according to theinvention of a damping device,

FIG. 4 shows diagrammatically a third version according to the inventionof a damping device,

FIG. 5 shows diagrammatically a fourth version according to theinvention of a damping device.

Contrary to the known embodiment illustrated in FIG. 1, according to theinvention the barrier air S is not routed through the damping device 20,but instead delivery ports 23′ and/or 23″ are provided and oriented inthe combustion chamber wall 10 such that the barrier air S flowingthrough the delivery ports 23′, 23″ flows over the resonator tube mouthM in the region of the combustion chamber inner wall virtually in asimilar way to film cooling.

FIG. 2 shows a first embodiment in which the resonator tube mouths M areset back in the combustion chamber wall 10 with respect to thecombustion chamber inner wall 10′ in a defined area 10″ away from thecombustion chamber inner space, and the delivery port 23′ is orientedsuch that the barrier air S is injected, virtually parallel to the flowdirection of the combustion gases G, into the space between the area 10″and the combustion chamber inner wall 10′ such that it flows completelyover the setback resonator tube mouths M of the resonator tubes 22. Inthis space in front of these resonator tube mouths M (shown here onlyfor two of the six resonator tubes), a barrier air film is thus formedwhich, even with a low mass flow of barrier air, very effectivelyprevents the penetration of hot combustion gases into the Helmholtzresonator 20. When injection of the barrier air takes place, asindicated in FIG. 2, through a tubular port 23′ in the upstream sidewall in the downstream direction of the combustion gases, the injectedbarrier air is entrained by the stream of combustion exhaust gases andan especially effective barrier film is thus obtained.

Since the effective axial distance of film cooling bores is limited, asecond delivery port 23″ lying opposite the first delivery port 23′ maybe provided, as indicated in FIG. 3, which is oriented such that thebarrier air S is injected virtually parallel to and opposite to the flowdirection of the combustion exhaust gases G so that even resonators witha greater extent in the flow direction can still be barred effectively.

If, as indicated in FIG. 4, the combustion chamber wall 10 has on thesetback area 10″, level with the combustion chamber inner wall 10′, anoverlap L with the setback areas 10″, the extent of the resonators canlikewise be increased, without an additional opposite row of barrier airbores being necessary.

It is advantageous if, as in FIG. 5, the delivery port 23′ or else otherdelivery ports, such as, for example, the delivery port 23″, shown inFIG. 3, is or are arranged in the combustion chamber wall 10 such thattheir axis A is inclined with respect to the resonator tube mouth M. Asa result, as well as barring, additional impact cooling of the resonatorwall is achieved, which may be expedient particularly in regions of thecombustion chamber where an especially large amount of heat isintroduced into the combustion chamber wall.

FIG. 2 to FIG. 5 show in each case various advantageous embodimentswhich individually or else in combination implement the idea accordingto the invention, to be precise that of ensuring an efficient andreliable barrier against the penetration of hot gases from thecombustion chamber into the damping devices without the passage ofbarrier air via the damping device. Moreover, the invention alsoembraces embodiments in which, contrary to the exemplary embodimentsshown, the deliveries of barrier air lie so near to the resonator tubemouths that they form a direct component of each of the resonator tubemouths and are thus virtually integrated into each resonator tube mouth.

1-6. (canceled)
 7. A combustion chamber for a gas turbine plant, thecombustion chamber includes: a combustion chamber wall, through whichcombustion gases flow in a direction of a following gas turbine; thecombustion chamber wall having a damping device for the damping ofthermoacoustic vibrations caused by combustion gases, the damping devicecomprising at least one Helmholtz resonator which is configured suchthat a resonator volume thereof lies on a side of the combustion chamberwall that faces away from an inner wall of the combustion chamber; theresonator has at least one resonator tube, the tube co-operates with theresonator volume, and the resonator tube has a mouth lying opposite theresonator volume in the combustion chamber inner wall and exits into thecombustion chamber; at least one delivery port configured for entry ofbarrier air into the combustion chamber in such manner as for barringthe resonator tube mouth the barrier air from a compressor plenum thatsurrounds the combustion chamber, the plenum being of a compressor thatis positioned upstream of the combustion chamber, and the at least onefirst delivery port being provided in a region of the combustion chamberwall near the mouth of the at least one resonator tube and the at leastone first delivery port being oriented such that the barrier air flowingthrough the at least one first delivery port flows over the resonatortube mouth; the resonator tube mouth is set back in the combustionchamber wall with respect to the combustion chamber inner wall and intoan area set back away from the combustion chamber, the at least onefirst delivery port is oriented and configured for injecting the barrierair virtually parallel to the flow direction of the combustion gases andflows over the setback resonator tube mouth.
 8. The combustion chamberas claimed in claim 7, wherein the resonator comprises a plurality ofresonator tubes and the resonator tubes have their respective mouthsoriented such that the barrier air of the delivery port flows over thesetback resonator tube mouths of the plurality of resonator tubes. 9.The combustion chamber as claimed in claim 8, further comprising asecond one of the delivery ports directed opposite to the first one ofthe delivery ports, the second one of the delivery ports being orientedsuch that the barrier air through the second one of the ports isinjected virtually parallel to and opposite to the flow direction ofcombustion gases in the combustion chamber and the barrier air throughthe second ones of the delivery ports flows over the setback resonatortube mouths.
 10. The combustion chamber as claimed in claim 7, whereinthe delivery port is oriented in the combustion chamber wall such thatthe delivery port axis is inclined with respect to the resonator tubemouth.
 11. The combustion chamber as claimed in claim 7, wherein thecombustion chamber inner wall has in a region of setback areas overlapswith the setback areas of the combustion chamber wall.
 12. A gas turbineplant with a compressor for the compression of sucked-in air, with thecombustion chamber as claimed in claim 7 following the compressor; andthe plant having a burner for admixing fuel and for the combustion ofthe fuel/air mixture, and an expansion turbine which follows the burnerand which converts the combustion exhaust gases of the burnt fuel/airmixture into mechanical energy.